1. Field of the Invention
The present invention relates to bis-crown-ether derivatives and their use, particularly the use for ion-selective membranes for potassium-selective electrodes or the like.
2. Description of the Prior Art
Generally speaking, ion-selective electrodes are those electrodes which indicate concentration or activity of a specific ion in a solution by membrane potential of membrane electrodes, as represented by glass electrodes for the measurement of pH.
Now, the potassium-ionic concentration in a living body has a close relation with metabolic reactions in the living body, and so the measurement of this ionic concentration is frequently utilized for the diagnosis of various diseases such as hypertensive diseases, renal diseases, nerval disturbances and the like, as well as the dialysis of blood. The measurement has hitherto been effected mainly by the use of the spectrum method such as flame analysis.
However, such spectrum method required not only a large-size instrument but also a significant amount of time for the measurement and accordingly was not suited for being carried out in the actual place of diagnosis. Thus there has been a continuing need for the development of a single method for the quick measurement of potassium ion and a small-size instrument. Although a method utilizing a liquid membrane comprising an antibiotic valinomycin as neutral carrier dissolved in an aromatic organic solvent has been put to practical use for this purpose, valinomycin is still a very expensive compound. Further, for the preparation of practical, useful potassium-selective electrodes, a high ionic selectivity for potassium ion not disturbed by sodium ion or ammonium ion which in many cases co-exists with the potassium ion is required.
The inventors of the present invention have already published on the ion-selective membranes for potassium-selective electrodes using, as neutral carrier, bis (15-crown-5) compounds containing benzo-crown rings (J. Electroanal. Chem., 95 (1979), 91-101). However, improvement in durability and response time of these electrodes has been required, though their high selectivity for potassium ion has been recognized.
The present invention has been made to solve these problems and the main purpose thereof resides in providing ion-selective membranes for potassium-selective electrodes, which use bis (15-crown-5) compounds containing a benzo-crown ring as neutral carrier and enable one to perform measurement of potassium ion simply and quickly for a long duration of time with high selectivity and accuracy.